7.8x+2.4x=20.4
10.2x=20.4
x=2
2(x+1)=6(两边÷2)
x+1=3
x=2
6(x-1.5)=15 两边÷3
2(x-1.5)=5
2x-3=5
2x=8
x=4
4x-12×3=100
4x=100+36
4x=136
x=34
(x-5)÷3=7
x-5=21
x=26
x-0.28x=3.6;0.72x=3.6;x=360/72;x=5
7.8x+2.4x=20.4
10.2x=20.4
x=2
2(x+1)=6(两边÷2)
x+1=3
x=2
6(x-1.5)=15 两边÷3
2(x-1.5)=5
2x-3=5
2x=8
x=4
4x-12×3=100
4x=100+36
4x=136
x=34
(x-5)÷3=7
x-5=21
x=26
x-0.28x=3.6;0.72x=3.6;x=360/72;x=5